PITTSBURGH — Pittsburgh Mayor Luke Ravenstahl said he has no firm plans after he leaves office at the end of the year, but he will remain in Pittsburgh. Ravenstahl spoke Thursday at the opening of a new supermarket in the city’s Hill District. He’s says a couple of potential employers have approached him, but he hasn’t accepted a job or been offered one. Ravenstahl was the youngest mayor in Pittsburgh’s history when he took office in 2006. He announced earlier this year that he wouldn’t seek re-election, saying he was tired of the pressures of public life. That was around the time that federal prosecutors began investigating members of his administration.